“Last count, eighteen. Kind of a hobby.” “Antique revolvers and rare truffles,” Remi replied. “You are an interesting man.”

Sam shoved the flare into one of his shorts’ cargo pockets, the Webley into the other, then began picking his way around the lagoon’s edge, hopping from boulder to boulder and doing his best to avoid wet patches, a task that became harder the closer he came to the waterfall. When he was within arm’s length of the cascade, he turned, gave a short wave to Remi and the Kid, then ducked into the deluge and disappeared.Four minutes later he reappeared, hopped onto a nearby boulder, shook the water from his hair, then made his way back to the beach.

“There’s a shallow grotto behind the falls,” he announced. “It’s about twenty feet deep and fifteen wide. It’s clogged with backwash-branches, rotting logs, heaps of grass that’ve formed into a loose dam-but behind all that I found an opening. It’s a horizontal gap, really, like a stone garage door that didn’t close all the way.”“There goes our streak,” Remi replied with a smile.

“Pardon me?” asked the Kid.

Sam said, “So far on this particular adventure, we haven’t had to go subterranean, which is rare, given what we do. Before there were barable doors and lockable vaults, if you wanted to keep something safe or a secret you had only two reliable choices: bury it or hide it in a cave.”Remi added, “Still pretty common today. Might have something to do with genetic memory: When in doubt, burrow.”

“So you’ve never had a completely aboveground adventure?”

Sam shook his head. Remi said, “It’s why we stay current on our climbing and spelunking skills.”

“Well, caves are far down my list of favorite places,” the Kid said. “So if you don’t mind, I’m going to let you two have all the fun. I’ll mind the fort.”

Ten minutes later, armed with the appropriate gear, Sam and Remi returned to the waterfall and ducked behind it into the grotto. The sunlight dimmed behind the curtain of water. They clicked on their headlamps.

Sam stepped close to Remi and said over the rush, “Stand to one side. I’m going to see if we’ve got any company. Be ready with a flare.”

Remi stepped to the other side of the grotto while Sam selected a long branch from the dam pile and pulled it free. Systematically, he began probing the debris, jamming the branch’s tip into holes and gaps and wiggling it about. He got no reaction; nothing moved. He spent another two minutes heel-kicking the larger logs, trying to illicit a response, but fared no better.“I think we’re okay,” Sam called.

They got to work, slowly dismantling the pile until they cleared a path to the rear wall. They knelt before the four-foot-tall gap. A shallow runnel trickled past their boots and across the grotto before joining the waterfall proper.

Sam jammed his branch into the opening and rattled it about. Again, nothing moved. He pulled the Webley from his pocket, leaned forward, pressed his face to the rock, and panned his headlamp from right to left. He straightened up and gave Remi the OK sign.“Once more into the breach,” she yelled.

“We two, we happy two,” Sam answered in kind.

“Nothing like a little bastardized Shakespeare to set the tone.”

MADAGASCAR, INDIAN OCEAN

THEIR ENTRY WAS THANKFULLY SHORT. AFTER FIVE FEET OF hunched walking, they saw that the rock ceiling abruptly sloped upward and found themselves standing in an elongated oval cavern a hundred feet wide with a thirty-foot-tall, stalactite-riddled ceiling. Their headlamps weren’t strong enough to penetrate more than thirty feet ahead, but from what they could see the space appeared to be loosely divided into “rooms” by mineral columns that shone pearlescent gray and butter yellow in the beams of their lamps. The quartz inclusions in the walls winked and sparkled. The floor, a mixture of jagged rock and silt that crunched under their boots, was split by a narrow, winding creek.“Seems like a natural place to start,” Sam said, and Remi nodded.

Using the creek’s path as a guide, they began moving into the cave.

“SOMEWHAT ANTICLIMACTIC,” Remi said after a few minutes. “I know. The day is young, though.”

Their last spelunking adventure had ended with not only the solution of the mystery of Napoleon’s lost cellar but also a discovery that was helping rewrite parts of ancient Greek history.

They continued on, covering a hundred feet, then two hundred. Sam’s headlamp picked out a wedge-shaped wall ahead from whose base the creek gushed. On either side of the wall, a tunnel curved back into darkness.“Your pick,” Sam said. “Left or right?”

“Right.”

They hopped over the creek and started down the right-hand tunnel. After twenty feet the floor sloped down, and they found themselves standing in calf-deep water. Sam shined his beam over the surface; there was a slight eddying current. They kept walking.Remi stopped and put her index finger to her lips.

She clicked off her headlamp. Sam did the same.

Then, following ten seconds of silence, a sound: something moving in the darkness ahead. Like leather scraping against stone. More silence, then another sound: like a heavy wet towel striking rock.

Sam and Remi looked at each other and, in near unison, mouthed: Crocodile . The leather was scaled skin rubbing on rock; the wet towel, a heavily muscled tail slapping stone. Splashing.Heavy feet plodded through water. Sam drew the Webley and pointed it into the darkness. Together, he and Remi clicked on their headlamps.

Twenty feet away and sloshing directly toward them was a crocodile snout; just behind the snout a pair of heavy-lidded eyes staring back at them. Farther back, at the edge of their headlamp beams, they could see a half dozen scaly bodies writhing about, eyes flashing, mouths agape, tails whipping.“Flare,” Sam said.

Remi didn’t hesitate. With a hiss, the tunnel filled with flickering red light. Remi lowered the flare to knee level and waved it before the oncoming crocodile, which stopped, opened its mouth, and let out a low hiss.“The Kid was right,” she said. “They don’t care for it.”

“For now. Start backing up. Slowly. Don’t turn your back on it.”

In lockstep, with Remi’s eyes fixed on the approaching crocodile, they began retreating. Sam glanced over his shoulder. “Another ten steps and we’re at the ramp, then the narrow part.”“Okay.”

“When we get there, plant the flare in the sand. We’ll see how they like that.”

When they reached the spot, Sam patted Remi’s shoulder. She knelt down, jammed the flare into the silt, then stood up and kept back-stepping, with Sam’s hand still on her shoulder. Halfway up the ramp, the crocodile stopped six feet before the hissing flare. It scrabbled first to the left, then to the right, then stopped again. It let out another hiss, then backed down the ramp and into the water. After a few seconds it disappeared from view.“How long do flares last?” Remi asked.

“That kind? Ten or fifteen minutes. With luck, long enough for us to check the other tunnel.”

“And if not?”

“Then we get to see how good I am with the Webley.”

PAUSING TO LISTEN every ten paces or so, they proceeded down the left-hand tunnel. After forty feet the tunnel suddenly broadened out into a roughly circular chamber. Remi’s headlamp swept over a dark elongated object on the floor. They both started and backpedaled ten steps, their feet skidding in the sand.Remi whispered, “Was it-”

“I don’t think so.” He took a deep breath and let it out. “Enough to get my heart going, though. Come on.”

They moved forward until their beams again found the object. “Looks like a rotted telephone pole,” Remi said.

And it did. But almost immediately Sam noticed what looked like a trio of wooden cross braces affixed to the pole, then bindings of some kind, mostly crumbled to dust but intact enough to retain their basic shape.“It’s an outrigger,” Remi whispered.